Ok. It means that you don't the user under which you are logged in has no access rights to that template. This could also happen due to some errors in the database, in that case you can try to login under user system, by setting password for that user in configuration -> user manager. It's possible that under system user that template will be visible.
The other thing you can try to do is stop netxms server and launch nxdbmgr check
The other thing you can try to do is stop netxms server and launch nxdbmgr check